1. Field of the Invention
The present invention, in general relates to automobile repair devices and, more particularly, to devices that are used to aid in replacing the pads of a disk brake.
Disk (or disc) brakes are well known and provide many benefits. It is necessary to replace the pads that are used with disk brakes from time to time. In order to do so, a piston in a caliper (i.e., a cylinder) must be pushed back into the caliper to make room to extract the worn pads and especially to allow room for the new pads to be installed. The new pads are thicker than the worn pads and, accordingly, the piston must be retracted an amount that is sufficient to accommodate the thicker replacement pads.
Prior art devices rely upon lead screws that push one of the pads outward, thereby retracting the piston into the caliper. The caliper normally includes one cylinder that pushes one of the pads toward a disk that is attached to a wheel of a vehicle and is disposed intermediate a second opposite pad. The caliper is disposed on a rail and is able to move from side to side and so the two pads are always aligned on opposite sides of the disk.
The only force that typically retracts the cylinder is any pressure exerted on the pads by the disk itself as it bears against the pads. This force then pushes the pads outward so that they are not in contact with the disk when brake pressure is removed (i.e., when a driver is no longer braking). The piston is retracted a small amount back in the caliper. As the pads wear, the piston may extend over one-half of an inch further out from the caliper than it did when the pads were new. Only a very small amount of retraction of the piston into the caliper normally occurs.
Accordingly, as the pads wear the piston extends as needed and the caliper automatically aligns itself so that the worn pads are disposed proximate the disk on each side thereof. To replace worn pads, the piston must be retracted fully back into the caliper.
Tools have been designed to do this but they tend to be either slow to use or expensive to purchase. Also, they typically require two hands to operate. Some such tools rely upon a lead screw that must be rotated. A rotational motion makes this process especially awkward to accomplish.
It is also desirable to be able to progressively vary the rate of retraction. Sometimes, the user will want to quickly retract the piston, such as when the pads are to be removed as quickly as possible. At other times, the user will want to steadily and slowly retract the piston, such as when the system is being tested for leaks or other failure modes.
Also, it is important to be able to stop retracting the piston and to maintain it at a particular position, for example when applying pressure to the brake pedal or otherwise testing the braking system.
Accordingly, there exists today a need for a disk brake tool that is able to easily and quickly retract a piston into a caliper and which is inexpensive to manufacture.
Clearly, such an apparatus would be a useful and desirable device.
2. Description of Prior Art
Brake tools are, in general, known. For example, the following patents describe various types of these devices:
U.S. Pat. No. 6,378,185 to Ratchovsky et al, Apr. 30, 2002;
U.S. Pat. No. 6,192,566 to Dunum, Feb. 27, 2001;
U.S. Pat. No. 5,479,689 to Schmitt et al., Jan. 2, 1996;
U.S. Pat. No. 5,018,261 to Markous, May 28, 1991; and
U.S. Pat. No. 3,835,522 to Ward, Sep. 17, 1974.
U.S. Pat. No. Design 457,795 to Mohammed et al., May 28, 2002.
While the structural arrangements of the above described devices, at first appearance, have similarities with the present invention, they differ in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior devices.
U.S. Pat. No. 3,705,581 to Drake, that issued Dec. 12, 1972 is a cast-spreading device that is known to the inventor but which solves a materially different purpose and is therefore not believed to be related to the field of the instant invention. It also fails to include elements that are essential to the functioning of the instant invention.
It is an object of the present invention to provide a disk brake tool that is economical to manufacture.
It is also an important object of the invention to provide a disk brake tool that is easy to use.
Another object of the invention is to provide a disk brake tool that is fast to use.
Still another object of the invention is to provide a disk brake tool that allows for a steady readily controllable progressive retraction of a cylinder into a brake caliper.
Still yet another object of the invention is to provide a disk brake tool that requires only one hand to operate, thereby freeing up a remaining hand.
Yet another important object of the invention is to provide a disk brake tool that does not introduce a rotational force.
Still yet another important object of the invention is to provide a disk brake tool that is able to hold the piston in a retracted position in the caliper at any location once pressure is removed from the tool.
Briefly, a disk brake tool that is constructed in accordance with the principles of the present invention includes a caliper gun frame, a lever attached to the frame, a rod that extends forward and away from a user as the lever is squeezed, a hollow extension shaft attached to the frame and disposed over a portion of the rod, a retaining plate attached to a distal end of the extension shaft, and a disk attached to a distal end of the rod.